1. Field of the Invention
The present invention relates to electronic musical instruments of a synthesizer type such as an electronic guitar, other electronic stringed instruments and the like, and more particularly to a technique for an electronic musical instrument for controlling an envelope of a musical tone to be generated.
2. Description of the Related Art
Recently, electronic musical instruments have been developed wherein a vibration of a plucked string is detected as an electric waveform signal, and a musical tone generating circuit comprising digital circuits and/or analog circuits is controlled in accordance with the detected waveform signal, and thereby a musical tone is synthesized and is acoustically generated.
In the other case, the above waveform signal can be electrically detected from a human voice or an acoustic signal generated by playing an acoustic instrument. There are following articles disclosing such a technique:
(a) U.S. Pat. No. 4,117,757 (issued on Oct. 3, 1978), inventor: Akamatsu.
This patent discloses an electronic circuit for forming a waveform signal in which "1" and "0" sequentially inverted at positive and negative peak points of an input waveform signal. This waveform signal is converted to a rectangular wave signal, and its frequency corresponds to a pitch of the input waveform signal.
(b) U.S. Pat. No. 4,606,255 (issued on Aug. 19, 1986), inventor: Hayashi et al.
This patent discloses a guitar synthesizer. A pitch is extracted for each string to obtain a corresponding voltage signal, and a musical tone signal is generated by voltage control.
(c) U.S. Pat. No. 4,644,748 (issued on Jan. 6, 1987), inventor: Takashima et al.
This patent discloses a technique for converting an acoustic signal input through a microphone into a digital signal, and extracting a pitch by digital processing.
(d) U.S. Pat. No. 4,688,464 (issued on Aug. 25, 1987), inventor: Gibson et al.
This patent discloses a technique for extracting a pitch in accordance with time intervals crossing three threshold levels, i.e., high, middle, and low threshold levels of an input waveform signal.
(e) Japanese Patent Publication No. 57-37074 (published on Aug. 7, 1982), applicant: Roland Kabhushiki Kaisha.
(f) Japanese Patent Publication No. 57-58672 (published on Dec. 10, 1982), applicant: Roland Kabushiki Kaisha.
The contents of these two patents correspond to the above-mentioned patent (a), U.S. Pat. No. 4,117,757, and disclose techniques for generating a rectangular wave having a frequency corresponding to a pitch of an input waveform signal.
(g) Japanese Patent Disclosure (Kokai) No. 55-55398 (disclosed on Apl. 23, 1980), applicant: Toshiba Corp.
This patent application discloses a technique for generating a rectangular wave having a frequency corresponding to a pitch of an input waveform signal as in the patent (a), U.S. Pat. No. 4,117,757.
(h) Japanese Patent Disclosure (Kokai) No. 55-87196 (disclosed on July 1, 1980), applicant: Nippon Gakki Seizo Kabushiki Kaisha.
This prior-art invention discloses a technique for generating a fundamental wave pulse having a period corresponding to a pitch in accordance with an output from a pickup of a guitar, counting the pulse by an interval counter to obtain period data, and converting the period data into digital frequency data.
(i) Japanese Patent Disclosure (Kokai) No. 55-159495 (disclosed on Dec. 11, 1980), applicant: Nippon Gakki Seizo Kabushiki Kaisha.
This prior-art invention discloses a technique wherein when an extracted pitch is not varied, a musical tone is started to generate. When two adjacent periods substantially coincide with each other, a coincidence signal is output, and start of tone generation is instructed in accordance with the coincidence signal.
(j) Japanese Utility Model Disclosure (Kokai) No. 55-152597 (disclosed on Nov. 4, 1980), applicant: Nippon Gakki Seizo Kabushiki Kaisha
This prior-art device discloses a technique wherein a vibration of a string is extracted by an optical pickup, and the vibration of the string is excited by a pick-up signal to obtain a vibration sustain effect.
(k) Japanese Utility Model Disclosure (Kokai) No. 55-162132 (disclosed on Nov. 20, 1980), applicant: Keio Gikken Kougyo Kabushiki Kaisha.
This prior-art device discloses a technique wherein a detector detects a next zero-cross point of positive and negative peak points of an input waveform signal, and a flip-flop is set/reset in response to each point detection to generate a frequency signal corresponding to a pitch.
(1) Japanese Patent Publication No. 61-51793 (published on Nov. 10, 1986), applicant: Nippon Gakki Seizo Kabushiki Kaisha. This patent is a publication of the invention (h), and has the same gist as the content of the invention (i). That is, digital frequency data is generated upon detection of a substantial coincidence between two adjacent periods.
(m) Japanese Utility Model Publication No. 62-20871 (published on May 27, 1987), applicant: Fuji Roland Kabushiki Kaisha.
This is a Japanese publication corresponding to the invention (b), U.S. Pat. No. 4,606,255.
(n) Japanese Patent Disclosure (Kokai No. 61-26090 (disclosed on Feb. 5, 1986), applicant: Seikou Denshi Kougyo Kabushiki Kaisha.
This prior-art invention discloses a technique for detecting a pitch from an input waveform signal, sequentially writing the detected pitch in a memory, and obtaining accurate pitch data later by executing an arithmetic operation.
(o) Japanese Patent Disclosure (Kokai) No. 62-163099 (disclosed on July 18, 1987), applicant: Fuji Gen Gakki Seizo Kabushiki Kaisha.
This prior-art invention relates to a guitar controller for a guitar synthesizer, wherein frequency changing methods are switched in accordance with monophonic or polyphonic tones generated. More specifically, when a monophonic tone is generated, a picked-up vibration period is continuously reflected to determine the frequency of the musical sound to be generated. When a polyphonic tone is generated, the vibration period is reflected at chromatic scale steps to determine the same.
Furthermore, the following U.S. patent applications disclosing an electronic stringed instrument and a relating electronic equipment thereto associated with the present invention assigned to the present assignee have been filed.
(p) U.S. Ser. No. 112,780 (filed on Oct. 22, 1987), abandoned in favor of Continuation application Ser. No. 07/478,759, filed Feb. 12, 1990 inventor: Uchiyama et al.
This prior-art invention discloses a technique for measuring a time period between positive and negative peak points or between zero-cross points associated with these peak points to extract a pitch of an input waveform signal based on the measured time period, and a technique for performing various control operations in accordance with the obtained pitch.
(q) U.S. Ser. No. 184,099 (filed on Apr. 20, 1988), now U.S. Pat. No. 4,817,484, issued Apr. 4, 1989 inventor: Iba et al.
In this prior-art invention, a musical tone parameter such as a timbre is designated by a fret operation and a picking operation of a string. In order to detect an operated fret, a pitch extraction technique, and a fret switch detection technique is used.
(r) U.S. Ser. No. 256,398 (filed on Oct. 7, 1988), inventor: Iba et al.
This prior-art invention discloses a technique for performing musical tone generation control in units of strings, changing characteristics of an output musical tone in accordance with a plucking strength of a string, or controlling an effector or pan (sound localization).
(s) U.S. Ser. No. 252,914 (filed on Oct. 3, 1988), now U.S. Pat. No. 4,841,827, issued June 12, 1989 inventor: Uchiyama
In this prior-art invention, a pitch extraction circuit comprises a digital circuit in place of a conventional analog circuit, and integration of the electronic circuit can be facilitated.
(t) U.S. Ser. No. 256,400 (filed on Oct. 11, 1988), now U.S. Pat. No. 4,895,060, issued Jan. 23, 1990 inventor: Matsumoto
This prior-art invention discloses an electronic apparatus for extracting a pitch from an input waveform signal and generating a musical tone having the corresponding tone pitch, and discloses a technique for changing a tone pitch of an output tone along with a change of the input waveform signal in pitch without accompanying an unnecessary variation in interval.
(u) U.S. Ser. No. 282,510 (filed on Dec. 9, 1988), now U.S. Pat. No. 4,924,746, issued May 15, 1990 inventor: Obata
In this prior-art invention, even if a pitch is unstably extracted at the beginning of tone generation, a musical tone having a stable pitch can be generated from the beginning. Start of musical tone generation is chromatically instructed on the basis of a pitch extracted by a pitch extraction system.
(v) U.S. Ser. No. 290,981 (filed on Dec. 28, 1988), now U.S. Pat. No. 4,928,563, issued May 29, 1990 inventor: Murata et al.
In this prior-art invention, strings are completely electronically tuned. Before a performance, a reference pitch is determined by plucking at a specific fret, and a tone pitch of a musical tone to be generated is determined on the basis of period data obtained by plucking at a designated fret using the reference pitch.
(w) U.S. Ser. No. 329,418 (filed on Mar. 27, 1989), inventor: Obata
In this prior-art invention, a signal intensity of an input waveform signal at its leading edge and a variation ratio of the signal intensity are detected and tone volume or timbre of a musical tone can be independently controlled in accordance with the two parameters. This technique, for example, in an electronic stringed instrument, allows to change only the timbre of the musical tone without changing its tone volume by shifting a string plucking position.
(x) U.S. Ser. No. 07/362,830 (filed on June 7, 1989) inventor: Katou
In this prior-art invention, characteristics of a musical tone, such as timbre, tone volume, tone pitch and the like are controlled on the basis of variation in a pitch frequency and thereby an abundant performance expression is realized.
As described above, according to the conventional technique, the form of the tone volume envelope of a musical tone to be generated is previously determined by selection of timbre of the musical tone and remains the same. Only the level of the whole tone volume envelope changes depending on the amplitude level of the input waveform signal at the leading edge.
Therefore, for example, even when a guitar operation is performed to abruptly change the envelope of the string vibration of an electronic stringed instrument, the envelope of a musical tone is determined regardless of the above guitar operation. Accordingly, a performance effect desired by the guitar player can not be obtained and the above guitar operation can cause sound offensive to the ear.
When the player plucks a string of an electronic musical instrument, the envelope of the string vibration has a characteristic shown at A in FIG. 1A, and the envelope of the musical tone to be generated has a characteristic shown at B in FIG. 1A. In FIG. 1A, a symbol "ON" indicates a timing at which sound generation of a musical tone is started when the level of the string vibration shown at A in FIG. 1A exceeds a predetermined value. Similarly, a symbol "OFF" indicates a timing at which an instruction to stop sounding is given when the level of the string vibration shown at A in FIG. 1A becomes equal to or less than a predetermined value. That is, the envelope of the musical tone to be generated decreases gradually after the OFF timing.
In this case, when the player performs a muting operation to compulsorily cease the string vibration by holding the string with the palm of his hand, while the string vibration has not adequately decreased after the string is plucked, the envelope of the string vibration shows a characteristic to rapidly decrease right after a strong attack, as shown at C in FIG. 1B. On the other hand, the envelope of the musical tone to be generated keeps an attenuating sound having considerable large volume for a long time even after the OFF timing. Therefore, staccato sounds are not generated and a unique nuance of the muting operation is lost.